Indexable cutting insert and holder therefor

ABSTRACT

A flat and centrally apertured wafer-like insert of cutting material provides a plurality of angularly spaced available cutting tips and is located edgewise against angularly related abutments upstanding from the inner edge of a supporting surface or platform against which the insert is clamped in the final seating in a conical end of the insert aperture of the mating conical head of a screw extending through the insert aperture and threading into a hole in the platform. The insert aperture is larger than the screw shank, and the outer end of the screw hole axis is inclined relative to the axis of the insert cone at a small angle and toward the abutment corner. As a result and in the final tightening of the screw after edgewise camming of the insert against said abutments, the screw shank bends laterally to allow seating of the coned screw head in the insert recess around substantially the full peripheries of the mating cones.

United States Patent Erkfritz [4 1 May 16, 1972 [54] INDEXABLE CUTTINGINSERT AND HOLDER THEREFOR [72] lnventor: Donald S. Erkfritz, Rockford,Ill.

[73] Assignee: The lngersoll Milling Machine Company,

Rockford, Ill.

[22] Filed: Mar. 9, 1970 21 Appl. No.: 17,605

3,354,526 11/1967 Erkfritz ....29/96 3,490,117 1/1970 Hertel ....29/963,142,110 7/1964 Hertel ....29/96 3,464,098 2/1969 Moore et al. "29/105Primary Examiner-Harrison L. Hinson Attorney-Wolfe, Hubbard, Leydig,Voit & Osann, Ltd.

[5 7] ABSTRACT A flat and centrally apertured wafer-like insert ofcutting material provides a plurality of angularly spaced availablecutting tips and is located edgewise against angularly related abutmentsupstanding from the inner edge of a supporting surface or platformagainst which the insert is clamped in the final seating in a conicalend of the insert aperture of the mating conical head of a screwextending through the insert aperture and threading into a hole in theplatform. The insert aperture is larger than the screw shank, and theouter end of the screw hole axis is inclined relative to the axis of theinsert cone at a small angle and toward the abutment corner. As a resultand in the final tightening of the screw after edgewise camming of theinsert against said abutments, the screw shank bends laterally to allowseating of the coned screw head in the insert recess aroundsubstantially the full peripheries of the mating cones.

7 Claims, 14 Drawing Figures INDEXABLE CUTTING INSERT AND HOLDERTHEREFOR BACKGROUND OF THE INVENTION This invention relates to theclamping to and the edgewise location on a supporting surface of anindexable insert of cutting material by means of a conically headedscrew extending through an aperture in the insert and acting, duringfinal tightening of the screw, to cam and press the insert edgewiseagainst at least one locating abutment and preferably against twoangularly related locating abutments upstanding from the inner edge ofthe platform, the diagonally opposing cutting edge of the indexableinsert being then left overhanging the platform for cutting engagementwith a workpiece.

Examples of indexable insert mountings of this general type are found inU.S. Pat. Nos. 2,598,581, 3,341,919 and 3,354,526.

SUMMARY OF THE INVENTION The primary object of the present invention isto greatly increase the ruggedness of indexable insert mountings of theabove character while employing standard screws and inserts of simpleand inexpensive construction. Generally stated, this objective isachieved by inclining the axes of the screw hole and the conical recessof the insert in which the screw head seats at a small angle relative toeach other and in a novel relation to the locating abutment or comerabutments, which relation, as permitted by lateral bending of theunsupported or free length of the screw shank in the final tightening ofthe screw after engagement of the insert with the abutments of itspocket, allows the conical head of the screw to seat in and aroundsubstantially the full periphery of the conical recess in the insert.Full peripheral surface contact between the screw head and insert isthus achieved instead of mere line contact as in the structures of theprior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of acylinder boring cutter having indexable inserts fastened to the body inaccordance with the present invention.

FIG. 2 is an exploded perspective view of one of the inserts and itsfastening screw.

FIG. 3 is a fragmentary section taken along the line 3-3 of FIG. 1. FIG.4 is a section taken along the line 4-4 of FIG. 2.

FIGS. 5 and 6 are sections similar to FIG. 3 showing different positionsof the screw being threaded into the body.

FIG. 7 is a fragmentary plan view of a part of FIG. 1.

FIG. 8 is a similar view omitting the insert.

FIG. 9 is a fragmentary view similar to FIG. 7 showing triangularinserts.

FIG. 10 is a fragmentary perspective view similar to FIG. 1 showing amodified form of locating abutment.

FIG. 11 is a fragmentary section taken along the line 11-11 of FIG. 10.

FIGS. 12 and 13 are perspective views of parts of the modifiedconstruction.

FIG. 14 is a fragmentary perspective view of a combined slab and facemilling cutter incorporating the insert fastening means of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the invention may be usedto advantage in securing indexable inserts of cutting material invarious types of cutter bodies to provide a number of available cuttingedges without resharpening, the invention has been found particularlyuseful in multiple blade boring cutters and therefore is shown and willfirst be described herein as embodied in such a cutter.

Referring then to FIGS. 1 to 8, a plurality of flat, wafer-like bladesor inserts 10 of suitable cutting material such as tungsten carbide areseated in pockets l1 equally and angularly spaced around the end of abody 12 centrally apertured for mounting on the end of a spindle (notshown) and adapted to be power rotated as indicated by the arrow and fedaxially to effect the boring or enlargement of a hole in a workpiece.Each of the pockets 11 is defined by a flat bottom surface or platform13 and by abutments 14 and 15 upstanding from the trailing and inneredges of the platform whose leading and outer corner 41 terminates at achip receiving recess 30. For use with the square ended inserts shown,the abutments 14 and 15 are preferably disposed at right angles to theplatform 13 and angularly related to define a comer for receiving andlocating one comer of the insert and so spaced inwardly from theperiphery of the body that the diagonally opposite comer of the insertwill overhang the leading edge of the platform and part of the chiprecess 30. The overhanging corner is thus adapted for cutting engagementwith the workpiece to be machined.

In the boring cutter illustrated, each insert 10 comprises a squareblock of cutting material with parallel side faces 17 and oppositeparallel ends 18 which are flat and perpendicular to the side faces. Theother straight and parallel ends 19 have opposite side edges 20 whichmay be beveled or rounded as shown and separated by flat surfaces 21narrower than the overall thickness of the wafer.

Each insert 10 is formed with a center hole 22 recessed at both ends inthe present instance to form frusto-conical seats 23 and 24 whose axes25 coincide and are disposed precisely perpendicular to the plane of theinsert. The cone angle of the seats, 60 in the form shown, is the sameas that of the underside 26 of the flat head 27 of a standard screw 28adapted to extend through the insert hole 22, thread into a mating hole29 in the body 12 at the center of the platform 13, and, in the finaltightening of the screw, clamp the insert against the platform withedges 18 and 19 of the insert in solid engagement with both of theabutments 14 and 15. Such tightening is effected by a tool engageable inan exposed center recess 31 in the screw head.

In accordance with the present invention, the cone angle of the screwhead surface 26 is the same as that of the surfaces of the recesses 23and 24, the minimum diameter 32 of the insert hole being somewhatgreater than the outside diameter of the screw shank 33, and the upperend 34a of the axis 34 of the screw hole 29 is inclined at a smallangle, preferably on the order of 1.5 to 5", relative to the axis 25 ofthe conical recesses 23 and 24 and toward the corner defined by theabutments I4, 15. This angle, indicated at X in FIG. 3, is such that inthe final tightening of the screw after engagement of one corner of theinsert against the abutments l4 and IS, the shank 33 of the screw willbend laterally to allow the screw head 27 to come into full surfaceengagement with and seat substantially around the full periphery of thesurface of the outer recess 23 as shown in FIG. 3.

It will be observed that with the insert hole 22 sized and shaped asabove described relative to the diameter of the screw shank 33, asubstantial length of the latter, indicated at b in FIG. 6, will beunsupported at the time when the screw head surface 26 first engages theinsert on the side of the recess 23 nearest the abutment comer. Thus,this length of the screw shank, usually about one to three times thediameter of the shank, is free to bend laterally as the screw isthreaded further into the hole. It has been found in practice that witha standard steel screw having a shank diameter of 0.187 of an inch, therequired lateral bending to allow full seating of the screw head (FIG.3) may be achieved without danger of stressing the steel above itselastic limit. If desired, the bending may be facilitated and thestressing reduced by countersinking the upper end of the screw hole asindicated in dot-dash outline in FIG. 3.

To achieve the lateral bending, the screw hole is formed in the platform13 with its axis 34 tilted within a generally upright diametrical plane36 (FIG. 7) extending transversely of the insert and platform anddisposed between a plane 37 bisecting the corner defined by theabutments l4, l5 and a plane 38 extending through the insert axis andperpendicular to the trailing abutment 14. In the tilting, the upper end34a of the screw hole axis 34 is moved toward the abutment l4 and awayfrom the axis 35 of the insert recess 23. Preferably, the screw holeaxis is inclined at from about L5 to 5 relative to the insert axis 35and desirably is positioned to intersect the axis of the located insertapproximately at a point 39 in the plane of the platform 13 as shown inFIGS. 3 and 5. I

With the screw and insert axes 34 and 35 located as above described, thebending of the screw shank 33 in the fastening of an insert on itsplatform 13 is illustrated on a somewhat exaggerated scale in FIGS. 3, 5and 6. First, the insert is placed on the platform 13 with one cornerdefining the desired cutting tip exposed beyond the platform and thediagonally opposite comer engaging the abutments 14 and 15. Next, thescrew shank 33 is projected through the insert hole as permitted by theample clearance at 32 and threading into the hole is started, the partsthen being positioned as shown in FIG. 5. As the shank is screwed intothe hole, the side of the conical head surface 26 nearest the abutment14 first engages the conical surface 23 of the insert on the sidethereof nearest the abutment 14 as shown in FIG. 6.

As the turning of the screw in the tightening direction is continuedfrom the position shown in FIG. 6, and the screw head is drawn furtherinto the recess 23, the first engaged side thereof acts against the headsurface 26 to cam the screw head laterally away from the abutment 14allowing the head to advance further into the recess 23. Such furtherentry of the screw head is permitted by lateral bending of theunsupported length b of the screw shank 33 within the clearance at 32around the hole of the insert. The bending continues until the head hasbecome fully seated and in engagement around substantially the fullperiphery of the screw head as illustrated in FIG. 3.

I With the screw hold axis 34 tilted in the plane 36 as above described,it will be apparent that the insert 10 will be crowded edgewise of theplatform 13 and toward the abutment corner by a resultant force whosecomponent directed toward the trailing abutment 14 is somewhat greaterthan the component 'directed toward the inner abutment 15. Since theresultant force acts along the plane 36, the insert will be heldsecurely against the locating abutments 14, and, by virtue of such fullperipheral surface seating, will be clamped and held much more securelyon the platform than has been possible with the screw clamps heretoforeused.

With the inserts 10 located by the abutments 14, 15 and clamped againstthe platforms 13 as above described, it will be apparent that theleading upper edge 42 and the end 43 at the intersecting beveled surfaceof the outer edge 19 will be positioned for cutting engagement with arough work bore. During counter-clockwise rotation and endwise axialfeeding of the body 12, these edges operate to remove a layer ofmaterial and enlarge the interior of the work hole to a diameterdetermined by the radial position of the tips 43 of the active cuttingedges. When square inserts are employed as in the boring cutterdescribed, the leading edges 18 which constitute cutting faces aredisposed at negative rake angles in order to dispose the outer edges ofthe inserts at angles that provide proper clearance for the cutting tips43. To provide proper clearance for the edges 42, the platforms aretilted somewhat so that their trailing ends are disposed below the pathstraversed by the edges 42.

By employing square inserts as above described with alined conicalrecesses 23 and 24 at both ends of the central aperture 22, it will beapparent that eight different cutting edges 42, 43 in preciselyidentical radial positions are available by indexing the inserts. Thatis to say, by indexing the insert around the platform from the positionshown in FIG. 2, a similar cutting edge defined by the diametricallyopposite tip indicated at c is brought into cutting position. Now, ifthe cutter is mounted on a bodyadapted for clockwise rotation, the othertips d and e at the corners of the same surface 17 may be brought intoactive position. By inverting the insert so that its opposite side willbe clamped to the platform, it will be apparent that four other cuttingedges 42, 43 will be available, two for left hand and two for right handrotation of the cutter body.

In boring cutters of the above character where the active cutting edgesare to act at positive rake angles, triangular inserts 45 mounted asshown in FIG. 9 may be used and crowded against locating comer abutments46, 47 by screws 48 arranged for lateral bending of their shanks intightening into conical recesses 49 of the inserts, the same as in theboring cutter described above.

For some machining operations, it is desirable to employ indexableinserts of other peripheral shapes, for example, inserts having arcuateor circular cutting edges. The screw bending and clamping action abovedescribed may be employed with such indexable inserts. In such a case,the corner defining abutments would engage arcuate portions of theinsert periphery.

In multiple bladed cutters adapted for finishing operations, it isdesirable to provide for great precision in the radial or axial locationof the active cutting edges and this, without the necessity of employingprecisely dimensioned and more costly inserts; The present invention, ina more detailed one of its aspects, contemplates mounting one of theholder corners defining the insert locating abutments for limitedadjustment transversely of the supporting platform and in the directionof the active cutting tip.

In the present instance, this is accomplished by making the innerlocating abutment 15, in the case of a boring cutter as shown in FIG. 1,in the form of a surface 51 mounted on the cutter body 12 in a planeinclined relative to the associated platform 13 and adapted for accurateadjustment transversely of the platform. Preferably, the inclinedsurface 51 is the inner face of a wedge 52 having a circularcross-section 53 at one end slidable in a cylindrical bore 54 extendinginto the cutter body adjacent the inner edge of the platform 13 and atan angle such as to adjust the abutment 51 broadwise as the wedge isadvanced into and out of the body.

Herein, such adjustment of the wedge is effected by a screw 55 havingoppositely threaded end portions 56 and 57 respectively threaded in ahole 58 extending longitudinally through the wedge and a hole 59extending into the cutter body at the bottom of the wedge recess 54. Byinserting a suitable tool in a recess 61 in the outer end of the screw,the latter may be turned in opposite directions to advance the wedgeinto and out of the cutter body and thus adjust the radial position ofthe abutment 15 defined by the side 51 of the wedge. By such adjustmentof the wedge of the different inserts while the latter are engagingtheir respective abutments 14 and 15, the wedges may be positioned toshift the inserts edgewise and outwardly and thereby locate the activecutting tips in precisely the same positions radially of the cutterbody. Similarly adjustable wedges 62 indicated in phantom may beincorporated and used for diameter adjustment of the boring cutter shownin FIG. 9.

The improved security achieved in locating and clamping indexableinserts in accordance with the present invention may be utilized withequal advantage in tool holders for use in various other types ofmachining. As an example, FIG. 14 shows a multi-blade cutter havingindexable inserts 63 clamped against platforms 64 spaced around theperiphery of a rotary body 65 and presenting, in each of the availablepositions of each insert, cutting edges 66 adapted, during rotation andbodily feeding of the cutter as indicated by the arrows, for so-calledslab milling of a flat surface and edges 67 for simultaneously facemilling a surface angularly disposed, for example at right angles, tothe slab milled surface. I

As before, the inserts 63 are centrally apertured and formed withfrusto-conical recesses 68 for receiving the heads 69 of standard screwsadapted to thread into holes 71 having axes 72 inclined relative to theplatforms 64 and toward abutments 74 in the same manner and at the sameangles as the axes 34 above described. Abutrnents 75 extending along thetrailing sides of the platforms cooperate with the abutments 74 todefine the comers into which corners 76 of the inserts 63 are crowded bytightening of the screws to bend the screw shanks in the same manner asin the boring cutter'described above.

In this milling cutter, the abutments 75 are formed by the leading faceof separately formed plates 77 disposed in slots 78 in the body 65 withopposite ends secured to the body as by welds 79. Such formation of theabutments 75 is advantageous in that, in the event of breaking of thecutter in service use, the plates 77 are the parts most likely to bedamaged thus providing for rebuilding of the cutter at minimum cost.

It will be apparent from the foregoing that by providing for bending ofthe screw shank 33 to allow for full seating of the conical screw head27 in the recess 23 of the insert, the latter is crowded into and heldin the abutment comer and held therein and against the supportingplatform by full peripheral surface engagement as contrasted with themere line contact used in the indexable insert holders of the prior art.

These advantages are achieved by the use of standard screws and low costinserts. At the same time, normal manufacturing variations in theconstruction and sizing of the insert and its center hole and in thelocation of the abutments l4, l5 and the axis of the screw hole arecompensated for automatically by automatic variations in theinterfitting of the parts of the screw head and the insert in the finaltightening of the screw.

1 claim:

1. In a cutting tool, the combination of, a body defining an insertreceiving pocket including a platform and a pair of angularly relatedabutments upstanding therefrom, a generally flat insert resting on saidplatform and having a center aperture with an upwardly flaringfrusto-conical recess providing a seat whose axis is normal to the planeof the insert, a plurality of cutting edges spaced around the peripheryof said insert equidistant from said axis and each adapted to be locatedin a cutting position outwardly beyond said platform by indexing of theinsert about said axis when an opposite edge of the insert is engagingsaid abutments, a screw having a frusto-conical head mating with thesurface of said recess and a shank of smaller diameter than saidaperture extending through said insert aperture and threading into anupright screw hole in the center of said platform, the outer end of theaxis of said screw hole being tilted at a small angle relative to theaxis of said seat and toward at least one of said abutments whereby upontightening of said screw the insert is cammed edgewise by the screw headengaging said seat and the screw shank is bent laterally, as permittedby the clearance within said aperture, to allow the screw head to comeinto substantially full peripheral surface engagement with said seat.

2. A cutting tool as defined in claim 1 in which said body is adaptedfor rotation and the tilting of said screw hole axis is in a planedisposed between a plane bisecting the corner defined by said abutmentsand a plane perpendicular to the trailing one ofsaid abutments.

3. In a cutting tool, the combination of, a body defining an insertreceiving pocket including a platform and at least one abutmentupstanding therefrom, a generally flat insert resting on said platformand having an aperture with an upwardly flaring frusto-conical recessproviding a seat whose axis is normal to the plane of the insert, aplurality of cutting edges spaced around the periphery of said insertand each adapted to be located in a cutting position by indexing of theinsert on said platform, a screw having a frusto-conical head matingwith the surface of said recess and a shank of smaller diameter thansaid insert aperture extending through said aperture and threading intoan upright screw hole in said platform, the upper end of the axis ofsaid screw hole being tilted at a small angle relative to the axis ofsaid seat and toward said abutment whereby upon tightening of said screwthe insert is cammed edgewise and toward said abutment by the screw headengaging said seat and the screw shank is bent laterally, as permittedby the clearance within said aperture, to allow the screw head to comeinto substantially full peripheral surface engagement with said seat.

4. A cutting tool as defined in claim 3 in which the length of saidscrew shank between said seat and the upper end of said screw hole isfree to bend laterally and allow said screw head to engage said seatsubstantially around the full periphery thereof in the final tighteningof the screw to clamp said insert against said platform.

5. A cutting tool as defined in claim 4 in which the unsupported lengthof said screw shank includes a length disposed within a recesscountersunk in said body at the upper end of said screw hole.

6. A cutting tool as defined in claim 3 in which opposite ends of saidinsert aperture are formed with frusto-conical recesses whose surfacesconverge axially toward each other to a diameter at their adjacent endsenough greater than the diameter of said screw shank to permit lateralbending thereof to allow full seating of the screw head in the outer oneof said recesses 7. In a cutting tool, the combination of, a bodydefining an insert receiving pocket including a platform and at leastone abutment projecting outwardly therefrom, a wafer-like cutting insertresting on said platform and having an aperture with an outwardlyflaring frusto-conical recess providing a seat whose axis is normal tothe plane of the insert, a plurality of cutting edges spaced around theperiphery of said insert and each adapted to be located in a cuttingposition by indexing of the insert on said platform, a screw having afrusto-conical head mating with the surface of said recess and a shankof smaller diameter than said insert aperture extending through saidaperture and into a screw hole opening outwardly of said platform, saidscrew head and screw shank being coaxial prior to tightening of saidscrew, the outer end of the axis of said screw hole being tilted at asmall angle relative to the axis of said seat and toward said abutmentwhereby upon tightening of said screw the insert is cammed edgewise andtoward said abutment by the screw head engaging said seat and the screwshank is bent laterally relative to the screw head, as permitted by theclearance within said aperture, to allow the screw head to come intosubstantially full peripheral surface engagement with said seat.

1. In a cutting tool, the combination of, a body defining an insertreceiving pocket including a platform and a pair of angularly relatedabutments upstanding therefrom, a generally flat insert resting on saidplatform and having a center aperture with an upwardly flaringfrusto-conical recess providing a seat whose axis is normal to the planeof the insert, a plurality of cutting edges spaced around the peripheryof said insert equidistant from said axis and each adapted To be locatedin a cutting position outwardly beyond said platform by indexing of theinsert about said axis when an opposite edge of the insert is engagingsaid abutments, a screw having a frusto-conical head mating with thesurface of said recess and a shank of smaller diameter than saidaperture extending through said insert aperture and threading into anupright screw hole in the center of said platform, the outer end of theaxis of said screw hole being tilted at a small angle relative to theaxis of said seat and toward at least one of said abutments whereby upontightening of said screw the insert is cammed edgewise by the screw headengaging said seat and the screw shank is bent laterally, as permittedby the clearance within said aperture, to allow the screw head to comeinto substantially full peripheral surface engagement with said seat. 2.A cutting tool as defined in claim 1 in which said body is adapted forrotation and the tilting of said screw hole axis is in a plane disposedbetween a plane bisecting the corner defined by said abutments and aplane perpendicular to the trailing one of said abutments.
 3. In acutting tool, the combination of, a body defining an insert receivingpocket including a platform and at least one abutment upstandingtherefrom, a generally flat insert resting on said platform and havingan aperture with an upwardly flaring frusto-conical recess providing aseat whose axis is normal to the plane of the insert, a plurality ofcutting edges spaced around the periphery of said insert and eachadapted to be located in a cutting position by indexing of the insert onsaid platform, a screw having a frusto-conical head mating with thesurface of said recess and a shank of smaller diameter than said insertaperture extending through said aperture and threading into an uprightscrew hole in said platform, the upper end of the axis of said screwhole being tilted at a small angle relative to the axis of said seat andtoward said abutment whereby upon tightening of said screw the insert iscammed edgewise and toward said abutment by the screw head engaging saidseat and the screw shank is bent laterally, as permitted by theclearance within said aperture, to allow the screw head to come intosubstantially full peripheral surface engagement with said seat.
 4. Acutting tool as defined in claim 3 in which the length of said screwshank between said seat and the upper end of said screw hole is free tobend laterally and allow said screw head to engage said seatsubstantially around the full periphery thereof in the final tighteningof the screw to clamp said insert against said platform.
 5. A cuttingtool as defined in claim 4 in which the unsupported length of said screwshank includes a length disposed within a recess countersunk in saidbody at the upper end of said screw hole.
 6. A cutting tool as definedin claim 3 in which opposite ends of said insert aperture are formedwith frusto-conical recesses whose surfaces converge axially toward eachother to a diameter at their adjacent ends enough greater than thediameter of said screw shank to permit lateral bending thereof to allowfull seating of the screw head in the outer one of said recesses.
 7. Ina cutting tool, the combination of, a body defining an insert receivingpocket including a platform and at least one abutment projectingoutwardly therefrom, a wafer-like cutting insert resting on saidplatform and having an aperture with an outwardly flaring frusto-conicalrecess providing a seat whose axis is normal to the plane of the insert,a plurality of cutting edges spaced around the periphery of said insertand each adapted to be located in a cutting position by indexing of theinsert on said platform, a screw having a frusto-conical head matingwith the surface of said recess and a shank of smaller diameter thansaid insert aperture extending through said aperture and into a screwhole opening outwardly of said platform, said screw head and screw shankbeing coaxial prioR to tightening of said screw, the outer end of theaxis of said screw hole being tilted at a small angle relative to theaxis of said seat and toward said abutment whereby upon tightening ofsaid screw the insert is cammed edgewise and toward said abutment by thescrew head engaging said seat and the screw shank is bent laterallyrelative to the screw head, as permitted by the clearance within saidaperture, to allow the screw head to come into substantially fullperipheral surface engagement with said seat.